Swim GP - Travessia Lisboa-Cascais

Lisbon awakens well before dawn on race morning, as the Belém Dock fills with the quiet intensity of swimmers prepping their gear and coordinating with support kayakers. This 20km ultra-marathon is a logistical feat, requiring every participant to have a dedicated escort for navigation and fueling across the changing currents of the Tagus and the Atlantic. The race demands a steady rhythm, beginning with the first 9km inside the river where ebb tide speeds often hit 1.5 to 2.5 m/s. Navigating this flow is a tactical challenge before reaching the open ocean for the final 11km push toward Pescadores Beach in Cascais.

Historical waters and landmarks

Passing the mid-river markers, athletes swim by the Bugio Lighthouse, a 16th-century fortification standing on a tiny islet that served as a vital maritime sentinel for centuries. The route continues toward the mouth of the estuary, where the Fort of São Julião da Barra dominates the horizon; once a key defensive bastion, it now guards the coastline with a different, more sedentary authority. As you navigate these waters, the legacy of the 1961 escape from the Caxias prison—where eight men fled in a modified armored vehicle—serves as a reminder of the dramatic history embedded in this shoreline. Along the route, you will also pass the medieval lime kilns of Paço de Arcos and the site from which Vasco da Gama once launched his caravels toward India.

Race day logistics

Organized annually by Swim GP, the event maintains a strict 100-swimmer capacity and an 8-hour time limit to ensure safety within the fluctuating tides. Athletes follow guidance buoys placed at 500-meter intervals, while support kayaks manage the four designated aid stations. The water temperature is generally mild in July, though the transition from river to ocean introduces shifting salinity and currents that require constant vigilance. Those seeking shorter distances or alternative seasonal challenges often look toward the Oeiras Open Water Race or the later Swim GP - Travessia Oeiras-Cascais for their late-summer training. The finish line at Pescadores Beach concludes a demanding point-to-point journey where the Tagus meets the Atlantic.